System and Method for Sampling Fluid from Piston Top Land Crevice of Piston Engine: 8,807,110

A system and method for sampling fluid from a top land piston crevice of a reciprocating piston engine. Access into the crevice is via a length of tubing inserted into a bore through the piston wall. Two valves, first a relief valve and then a piloted check valve, operate together to capture a sample of fluid from the crevice at a time just before TDC of the piston on its compression stroke. The sampled fluid flows from the check valve into a sample container. The valves further cooperate to close fluid communication from the crevice after a sample is taken, which allows the engine to operate normally.